科研之友
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摘要
In this paper, lower boundaries at which a liquid-centered swirl coaxial injector switches from nonpulsatile behavior to self-pulsation are experimentally resolved under water and air flow conditions for an element configured both with and without inner post recess. Data-based modal decomposition analyses are used to extract distinct near-field spray dynamics from high-speed schlieren imagery. Self-pulsation is found to be instability-induced by gas-liquid interactions that strip liquid from the contiguous spray cone. These interactions take place in a regime where coaxial flows are known to experience fiber-type breakup due to hydraulic and aerodynamic instabilities. Periodic, nonpulsatile spray breakup patterns are detected as a precursor to self-pulsation. The frequency of these nonpulsatile patterns ranges from approximate to 1-4kHz and compares well with the frequency of self-pulsation at its onset, which directly supports conventional ideas related to the mechanism of self-pulsation. The transition of spray dynamics from nonpulsatile to self-sustained oscillations shows a destabilizing/stabilizing effect as gas velocity increases, establishes temporally unstable spray oscillation at onset, and suggests that self-pulsation may be excited when stripping behavior engages one or more fluid oscillators of the injector element.
- 出版日期2017-11
